A New Tunable Coherent FIR-THz Source

Bloch oscillations are one of the most basic effects in
solids: If an electron is put into a static field, it will
accelerate until it reaches the edge of the first Brillouin
zone. It is then Bragg-reflected and returns to its original
position, where it starts to accelerate again. The resulting
spatial oscillation has never been observed in
bulk solids since it is suppressed by scattering events.
Bloch oscillations have recently been observed in semiconductor
superlattices. These experiments demonstrate that the frequency of the oscillations is tunable
over a large range by the static electric field and that the
electron oscillations lead to emission of THz radiation,
which is promising for applications.